Structural properties of ultra-low density nanoholes for the generation of well-separated GaAs quantum dots

Abstract

We apply the local droplet etching (LDE) technique in a conventional molecular beam epitaxy system for self-organized nanohole formation on AlGaAs surfaces. By optimizing the arsenic flux during the Al droplet deposition the hole density can be reduced down to the 106cm−2 regime. The nanohole shape and density are tunable in a wide range by the amount of droplet material deposited and the initial holes are customized by overgrowth with AlGaAs of varied thickness. Nanoholes with controlled depths from 30 down to a few nanometers are fabricated, while the ultra-low density is sustained. These nanoholes are filled with GaAs to form well separated GaAs QDs, with size precisely controlled by the filling level. Studies of the optical emission of single dots exhibit sharp excitonic lines at low and a clear shell structure at high excitation power. In particular, the quantization energies in dependence of the QD size are measured.